1. Field of the Invention
The present invention relates to a double flywheel, especially for a motor vehicle, comprising two coaxial rotatable masses which are mounted for rotational movement of one with respect to the other about a common axial axis of symmetry, with coupling means being interposed operatively between the two masses.
2. Description of the Related Art
It is known from French patent No. 96 03231 filed on Mar. 14, 1997 to provide a double flywheel, in particular a damped double flywheel for a motor vehicle, comprising two coaxial rotatable masses which are mounted for rotary movement of one with respect to the other about a common axial axis of symmetry, with, interposed operatively between the two masses, coupling means and axially acting friction means, which are carried mostly by one of the masses, wherein a first one of the two masses is adapted to be coupled in rotation to a driving shaft, while the second of the two masses is adapted to be coupled in rotation disconnectably to a driven shaft and includes a plate (20) constituting the reaction plate of a friction clutch, and wherein the second mass is mounted for rotation on the first mass, and of the type in which the friction means comprise:
a control ring, referred to as the first friction ring, a portion of which is arranged to engage frictionally on a friction face of the said one of the masses, and which is coupled in rotation to the other one of the two masses; PA1 a friction ring, referred to as the second friction ring, situated radially outwardly of the control ring, which meshes with the control ring with a circumferential clearance, and which is biased into contact with the said friction face; and PA1 a closure ring fixed to the said one of the two masses, the control ring and the friction ring being placed axially between the said friction face of the closure ring. PA1 the outer peripheral portion of the control ring is arranged to engage frictionally, firstly on the said friction face and secondly on the closure ring, which biases the control ring through its outer periphery, the control ring being gripped elastically between the said friction face and the inner periphery of the closure ring; PA1 the control ring has at its outer periphery two annular working friction surfaces, in particular radial or circumferential corrugations, which are offset axially and which are arranged to engage frictionally, firstly on the said friction face and secondly on the closure ring; PA1 the closure ring has at its outer periphery a generally transversely oriented flange, for fastening the friction ring to the said one of the two masses, and which is joined, in particular by an axially oriented zone, to a generally radially oriented base, which is centrally perforated and which is inclined towards the said one of the two masses in such a way that there exists, between the outer periphery of the base and the said friction face, an axial distance which is greater than the axial distance between the inner periphery of the base and the said friction face; PA1 the axial distance between the two working friction surfaces, in particular between two opposed top surfaces of the corrugations, of the control ring is greater than the axial distance between the inner periphery of the base and the said friction face; PA1 the friction ring is subjected to the action of an axially acting resilient ring which bears directly on the closure ring so as to bias the friction ring into contact with the said friction face; PA1 the resilient ring is fixed to the closure ring for rotation therewith; PA1 the resilient ring includes at its outer periphery inclined radial lugs which engage within press-formed projecting elements of the control ring; PA1 the friction ring has at its inner periphery lugs by means of which it meshes with complementary portions of the control ring; PA1 the working friction surfaces of the control ring are corrugations, the top surfaces of which constitute the working friction surfaces of the control ring, which are in permanent frictional contact against the said friction face and against the closure ring, and the lugs of the friction ring mesh with the corrugations; PA1 the working friction zones of the control ring are two radially offset annular zones, and the control ring includes, radially outwardly and beyond its outer periphery, lugs which mesh with the lugs of the friction ring; PA1 the said one of the two masses is the said first mass.
Thanks to the friction means, the design proposed in that document enables vibrations to be damped out by creating permanent friction, generally at a low level, so as to damp out vibrations, particularly in the slow running mode of the engine, and, beyond this slow running mode, to create differentially friction of higher intensity, the damped flywheel remaining very simple and having a reduced number of components.
In general terms, the permanent friction enables small oscillations to be damped out, while the differential friction enables larger oscillations to be damped out.
The design of the damping means proposed in that document does however have the disadvantage that it calls for a high number of components, which, apart from their number and their cost, greatly complicates the operation of assembling them together.
Thus, each of the first friction ring and the second friction ring is associated with an application ring and an axially acting resilient ring, these four additional components being interposed axially between the two associated friction rings and the closure ring.
An object of the present invention is to overcome these disadvantages and to respond to these requirements in a simple and inexpensive way.
It is therefore an object of the invention to reduce the number of components in the friction means.
According to the invention, a double flywheel of the type described above is characterised in that the control ring is arranged to engage frictionally, firstly on the said friction face, and secondly on the closure ring, and in that the control ring is gripped elastically between the said friction face and the closure ring.
According to further features of the invention:
The following description illustrates the invention with reference to the attached drawings, in which: